Ant mosaics occur in SE Asian oil palm plantation but not rain forest and are influenced by the presence of nest‐sites and non‐native species

Interaction networks within biotic communities can be dramatically altered by anthropogenic habitat modification. Ants, an important ecological group, often interact competitively to form mosaic‐like patterns in disturbed plantation habitats, in which dominant species form mutually exclusive territories. However, the existence of these ant mosaics in pristine forests is contentious. Here we assess the relative strengths of ant competitive interactions in oil palm plantation and primary rain forest in Sabah, Malaysia, using null models of species co‐occurrence. We use two metrics: the C‐score, which measures mean degree of overall co‐occurrence, and a novel metric, the C_var‐score, which measures the variance in degree of co‐occurrence. We also investigate the role of nest sites by collecting ants from canopy and leaf litter microhabitats, and from epiphytic ferns, an important nest site for canopy ants. Furthermore, we assess whether non‐native species, which were widespread in oil palm plantation (61 occurrences vs five in rain forest) are important in driving the formation of ant mosaics. We found no evidence for ant mosaics in any primary forest microhabitat. In oil palm plantation, segregation between species was pronounced in epiphytes, weak in the rest of the canopy and absent in leaf litter communities. Intriguingly, exclusion of non‐native ant species from analyses increased the degree of negative species co‐occurrence in all three microhabitats, with species segregation in the oil palm canopy becoming statistically significant. Our results suggest that invasion of plantation habitats by non‐native species does not drive increased species segregation in ant communities. Rather, high degrees of species segregation might relate to changes in the importance of canopy nest sites, with colonies competing more strongly for these in plantations. In primary forests, weaker nest‐site limitation and the highly complex, more vertically stratified, non‐uniform canopy could lead to random co‐occurrence between ant species at the scales studied here.     

Difference in seasonal activity pattern between non-native and native ants in subtropical forest of Okinawa Island,Japan

Biological invasions by non-native tramp ants are reported throughout the world, particularly in island ecosystems. In Okinawa Island, a subtropical island in south-western Japan, many tramp ants including the invasive ant, Anoplolepis gracilipes, already occur. In this study activity patterns of the ground-foraging tramp and native ants were investigated for one year by using food bait traps at the forest edges where both categories of ants coexist. On a seasonal time scale, activity patterns were different between exotic and native ants. Native ants are active and seemingly more dominant from spring to summer whereas tramp ants become more dominant from autumn to winter. These results suggest there might be temporal niche partitioning between tramp and native ants, and native ants might be able to dominate tramp ants in their suitable seasons.     

Fuelling the biodiversity crisis: species loss of ground-dwelling forest ants in oil palm plantations in Sabah,Malaysia (Borneo)

Oil palm plantations today cover large areas of former tropical lowland rain forest in Southeast Asia and are rapidly expanding on the island of Borneo. Study of the community of ground-dwelling ants in different plantations in Sabah, Malaysia, over 2 years using tuna baiting, revealed that the oil palm plantation ground ant community was severely reduced in species richness in comparison to the forest interior, regardless of age, undergrowth cover, or proximity to neighbouring forest. The results indicate that oil palm plantation habitats, now covering more than 15% of Sabah’s land area, can sustain only about 5% of the ground-dwelling ant species of the forest interior. Nine of the 23 ant species baited in the plantations were never recorded inside forest. All numerically dominant ants were non-forest species. The most common species was Anoplolepis gracilipes, an invasive species present at 70% of all bait sites and known to cause ‘ecological meltdowns’ in other situations. The low frequency and species number of forest ground ants indicates that oil palm plantations act as effective dispersal barriers leading to community isolation in rain forest remnants. The replacement of natural forests with oil palm plantations poses a serious threat to the conservation of biodiversity on Borneo if similar results are confirmed in other taxa.     

Colonisation by a dominant ant facilitated by anthropogenic disturbance: effects on ant assemblage composition, biomass and resource use

Dominant species are thought to regulate species composition and assemblage structure. Invasion by a dominant species is thus likely to alter assemblages and anthropogenic disturbance often facilitates such invasions. In this study we examined the association of a dominant ant, Iridomyrmex purpureus , native to south-eastern Australia, with fire trails in national parks and its effects on ant assemblages. Association with fire trails was examined by comparing the numbers of I. purpureus nests on transects along fire trails with those in transects through surrounding vegetation. Ant assemblages and habitat characteristics of eight sandstone outcrops that supported colonies of I. purpureus were compared with those on eight that did not in summer and autumn 2000. We examined ant species richness, abundance, composition and biomass using quadrats, and resource use with Acacia botrycephalus seeds placed on rock and in vegetation. I. purpureus nests were considerably more common along fire trails than in surrounding vegetation. Sites with I. purpureus had similar species richness to those without, but a lower abundance and biomass of other ants and a different assemblage composition. These differences could not be attributed to any differences in measured habitat characteristics. Ecologically similar species, particularly other species of Iridomyrmex , were less abundant in areas with I. purpureus . While the biomass of other species was suppressed in areas with I. purpureus , the biomass of the dominant was several times that of the assemblage of other ants, a pattern shared with assemblages invaded by exotic species. In areas with I. purpureus , seeds were removed more rapidly from rock, but not vegetation, indicating that resources on rock may be under-exploited by other species. Regulation of invaded ant assemblages by this dominant ant is thus limited to functionally similar species, and this may be due to its use of resources that are unexploited in its absence.     

Effect of an exotic Acacia (Fabaceae) on ant assemblages in South African fynbos

Ant assemblages in South African fynbos invaded by Acacia saligna were compared with ant assemblages in undisturbed fynbos to determine whether ant assemblages change under exotic plants that produce ant‐dispersed seeds. Overall, no differences in the species richness of ants were found between weed‐infested and native sites but there were differences in both ant abundance and the composition of the ant assemblage. Ants were much less abundant in weed‐infested sites. To investigate whether changes in ant assemblages in weed‐infested areas could be due to a preference for native seeds over exotic seeds, seeds of a range of species were offered to ants and ants that handled seeds were identified. Thirteen species of ants handled A. saligna seeds and there was no evidence to suggest that the ant assemblage as a whole preferred native seeds to A. saligna seeds. Hypotheses that may account for this pattern are discussed.     

Competitive dominance in the organisation of Mediterranean ant communities

1. Competition by dominant species is thought to be key to structuring ant communities. However, recent findings suggest that the effect of dominant species on communities is less pronounced than previously assumed. 2. The aim of the present study was to identify the role of dominant ants in the organisation of Mediterranean communities, particularly the role of competition in invaded and uninvaded communities. The effects on ant assemblages of two dominant ants, the invasive Argentine ant and the native ant, Tapinoma nigerrimum Nylander, were assessed. 3. The abundances of both dominant ants were significantly correlated with a decrease in native ant richness at traps. However, only the invasive ant was associated with a reduction in diversity and abundance of other ant species at site scale. In the presence of T. nigerrimum, species co‐occurrence patterns were segregated or random. Community structure in both the dominant‐free and the Argentine ant sites showed random patterns of species co‐occurrence. 4. The present findings indicate that dominant ants regulate small‐scale diversity by competition. However, at the broader scale of the assemblage, T. nigerrimum may only affect species distribution, having no apparent effect on community composition. Moreover, we find no evidence that inter‐specific competition shapes species distribution in coastal Mediterranean communities free of dominant ants. 5. These results show that dominant species may affect ant assemblages but that the nature and the intensity of such effects are species and scale dependent. This confirms the hypothesis that competitive dominance may be only one of a range of factors that structure ant communities.     

Oil palm expansion into rain forest greatly reduces ant biodiversity in canopy,epiphytes and leaf-litter

Oil palm cultivation is expanding rapidly into many of the world's most biodiverse tropical regions. One of the most functionally important and ecologically dominant animal groups in these environments is the ants. Here, we quantify the overall impacts of clear-felling lowland dipterocarp rainforest and conversion into oil palm plantation on ant diversity. At study sites in Sabah, Malaysia we collected ants from three microhabitats: 1 – the canopy, 2 – bird's nest ferns (Asplenium nidus complex, a common epiphyte in forest and oil palm), and 3 – leaf litter. We also measured temperature, humidity and light at collection sites to assess their impacts on ant community composition. Total ant species richness decreased from 309 to 110 (?64%) between forest and oil palm plantation. However, this impact was not the same across all microhabitats, with bird's nest ferns maintaining almost the same number of ant species in oil palm compared to forest (forest-oil palm, ferns: 36–35 (3% loss), canopy: 120–58 (52% loss), leaf litter: 216–56 (74% loss)). Relative abundance distributions remained the same for fern-dwelling ants, but became less even for oil palm ants in both the canopy and the leaf litter. These differences may be due in part to the ability of bird's nest ferns to provide a stable microclimate in hot, dry plantations. We also found that non-native ant species were more abundant in oil palm than in forest, and few forest ant species survived in plantations in any of the microhabitats. Only 59 of the 309 forest species persisted in oil palm plantations, corresponding to an 81% loss of forest species resulting from habitat conversion. Although oil palm supports many more ant species than has been previously reported, converting forest into plantation still leads to a dramatic reduction in species richness. The maintenance of forested areas is therefore vital for the conservation of ant biodiversity.     

Imported crazy ant displaces imported fire ant, reduces and homogenizes grassland ant and arthropod assemblages

A recently introduced, ecologically dominant, exotic ant species, Nylanderia fulva, is invading the Southeastern United States and Texas. We evaluate how this invader impacts diversity and abundance of co-occurring ants and other arthropods in two grasslands. N. fulva rapidly attains densities up to 2 orders of magnitude greater than the combined abundance of all other ants. Overall ant biomass increases in invaded habitat, indicating that N. fulva exploits resources not fully utilized by the local ant assemblage. At high density, as N. fulva spreads, it eliminates the current ecologically dominant invasive ant, red imported fire ants (Solenopsis invicta). Compared to imported fire ant dominated habitat, N. fulva invasion zones have lower non-ant arthropod species richness and abundance with impacts differing by trophic category. Further, N. fulva reduces abundance and species richness of the remainder of the ant assemblage and does so in a non-random manner: impacting species with small sized workers much less than species with larger workers. In these and other ant assemblages with a large exotic component, the exotics tend to be small bodied species. As a result, N. fulva almost completely eliminates regionally distributed species, but leaves globally distributed species largely unaffected, thereby systematically favoring introduced over native diversity. S. invicta impacts wildlife and arthropod assemblage structure and is nearly ubiquitous in non-forested habitats of the Southeastern United States and Texas. Its displacement by N. fulva has critical implications for the natural systems of this region.     

Distinctive life traits and distribution along environmental gradients of dominant and subordinate Mediterranean ant species

For most animal and plant species, life traits strongly affect their species-specific role, function or position within ecological communities. Previous studies on ant communities have mostly focused on the role of dominant species and the outcome of interspecific interactions. However, life traits of ant species have seldom been considered within a community framework. This study (1) analyses life traits related to ecological and behavioural characteristics of dominant and subordinate ant species from 13 sites distributed throughout the Iberian Peninsula, (2) determines how similar the ant species are within each of the two levels of the dominance hierarchy, and (3) establishes the distribution patterns of these different groups of species along environmental gradients. Our results showed that the differences between dominants and subordinates fall into two main categories: resource exploitation and thermal tolerance. Dominant species have more populated colonies and defend food resources more fiercely than subordinates, but they display low tolerance to high temperatures. We have identified different assemblages of species included within each of these two levels in the dominance hierarchy. The distribution of these assemblages varied along the environmental gradient, shifting from dominant Dolichoderinae and cryptic species in moist areas, to dominant Myrmicinae and hot climate specialists mainly in open and hot sites. We have been able to identify a set of life traits of the most common Iberian ant species that has enabled us to characterise groups of dominant and subordinate species. Although certain common features within the groups of both dominants and subordinates always emerge, other different features allow for differentiating subgroups within each of these groups. These different traits allow the different subgroups coping with particular conditions across environmental gradients.     

Dominant ants can control assemblage species richness in a South African savanna

1. Competition is considered a key factor structuring many communities, and has been described as the 'hallmark' of ant ecology. Dominant species are thought to play a key role structuring local ant assemblages through competitive exclusion. 2. However, while there have been many studies demonstrating competitive exclusion and consequently reduced richness at baits, it is not clear whether such regulation of 'momentary' diversity at clumped food resources can scale up to the regulation of richness at the site or assemblage level. 3. In this study, ant assemblages were sampled in three different savanna habitats in South Africa using both baiting and pitfall trapping. 4. As has been found in previous studies, there was a unimodal relationship between dominant ants and species richness at baits, with high abundances of dominant ants regulating species richness through competitive exclusion. Analysis of pitfall samples revealed strong convergence in pattern, and results from null model co-occurrence analyses supported the findings. 5. The importance of competition in structuring local ant assemblages was, however, only apparent at one of the three savanna habitats suggesting that a full range of extreme environments is needed to produce the full unimodal relationship at the assemblage level. 6. Although the relative importance of competition varied with habitat type, the study demonstrated that in some habitats, dominant ants can control species richness at the assemblage level.     

Diversity, evolutionary specialization and geographic distribution of a mutualistic ant-plant complex: Macaranga and Crematogaster in South East Asia

The most conspicuous and species-rich ant-plant mutualism in the Malesian region is found in the important pioneer tree genus Macaranga , yet little is known about the identities or community ecology of the species involved. Our studies have revealed a far more complex system than previously thought. This paper presents the first extensive investigation in the whole distribution area of myrmecophytic Macaranga. All ant-inhabited species were restricted to the moister parts of SE Asia: Peninsular Malaysia, South and East Thailand, Sumatra and Borneo. We found a rather strict and similar altitudinal zonation of myrmecophytic Macaranga species in all regions. Here we focus on the majority of the 19 Macaranga species obligatorily associated with ants of the genus Crematogaster. We identified a total of 2163 ant queens which belonged to at least eight (morpho)species of the small subgenus Decacrema as well as to one non-Decacrema (probably from Atopogyne ). The ant species were not randomly distributed among the Macaranga species but distinct patterns of associations emerged. Despite common sympatric distribution of Macaranga species, in most cases a surprisingly high specificity of ant colonization was maintained which was, however, often not species-specific but groups of certain plant species with identical ant partners could be found. These colonization patterns usually but not always mirror existing taxonomic sections within the genus Macaranga. Possible mechanisms of specificity are discussed. The results are compared with other ant-plant mutualisms.     

Limited effects of dominant ants on assemblage species richness in three Amazon forests

1. Ants are highly interactive organisms and dominant species are considered to be able to control the species richness of other ants via competitive exclusion. However, depending on the scale studied, inter‐specific competition may or may not structure biological assemblages. To date, ant dominance–richness relationships have only been studied in small sample units, where a few dominant colonies could plausibly control most of the sample unit. 2. We conducted a comprehensive survey of terrestrial ant assemblages using bait, pitfall, and litter‐sorting methods in three sites in Brazilian Amazonia. Using a spatially structured rarefaction approach, based on sampling units with linear dimensions ranging from 25 to 250 m, the mesoscale patterns of ant dominance–richness relationships (sampling units covering hundreds of meters separated by kilometers) were investigated. 3. Interference–competition models (parabolic or negative linear relationships between species richness and the abundance of dominant ants) tended to be more frequent in smaller sample units or in assemblages sampled with interactive methods, such as baits. Using more inclusive sampling methods, the relationship was generally asymptotic rather than parabolic, with no reduction in species diversity because of the presence of dominants. Random co‐occurrence patterns of species within sites support the interpretation of a limited role for present‐day competition in structuring these assemblages. 4. Competition from dominant species may reduce species richness in small areas, especially when artificial baits are used, but appears to be less important than environmental constraints in determining ant species richness across scales of hectares and greater in these Amazon forests.     

Responses of tropical fruit bats to monoculture and polyculture farming in oil palm smallholdings

The oil palm industry is one of the main economic drivers in Southeast Asia. The industry has caused tropical deforestation on a massive scale in producing countries, and this forest conversion to oil palm agriculture has decimated the habitat of numerous native species. Monoculture and polyculture practices are two distinctive oil palm production systems. We hypothesize that polyculture farming hosts a greater diversity of species than monoculture farming. Habitat complexity in smallholdings is influenced by multiple farming practices (i.e. polyculture and monoculture). However, little is known about the effects of such farming practices in smallholdings on mammalian biodiversity, and particularly frugivorous bats. Our study aimed to find the best farming practice to reconcile oil palm production with biodiversity conservation. Mist-nets were used to trap frugivorous bats at 120 smallholdings in Peninsular Malaysia. We compared species richness and the abundance of frugivorous bats between monoculture and polyculture smallholdings. We investigated their relationships with vegetation structure characteristics. Our results revealed that species richness and abundance of frugivorous bats were significantly greater in polyculture smallholdings than monoculture smallholdings. We also found that 28.21% of the variation in species richness was explained by in situ habitat characteristics, including the number of dead standing oil palms and immature oil palms, non-grass cover, height of non-grass cover, and farming practices. The in situ habitat quality was closely associated with oil palm farming management. Commercial growers should implement polyculture rather than monoculture farming because polyculture farming has positive effects on the abundance and species richness of bats in oil palm production landscapes.     

Habitat differences and occurrence of native and exotic ants on Okinawa Island

Ant fauna on Mallotus japonicus, a shrub with extrafloral nectaries, was investigated in two types of habitat (the villages and the forest‐edges) on subtropical Okinawa Island, Japan. Twenty and 16 ant species were found, including 11 and 6 tramp species in the villages and in the forest‐edges, respectively. Occurrence of tramp species was higher in the villages than in the forest edges, supporting the idea that tramp species tend to dominate in disturbed habitats. Nevertheless, the richness of native ants was almost the same across the two habitat types. Consequently, the ant species diversity on M. japonicus appeared higher in the villages. However, monitoring has to be continued to determine whether the above findings represent a stable phenomenon of the community or just a temporary state.     

Are Local Filters Blind to Provenance? Ant Seed Predation Suppresses Exotic Plants More than Natives

The question of whether species’ origins influence invasion outcomes has been a point of substantial debate in invasion ecology. Theoretically, colonization outcomes can be predicted based on how species’ traits interact with community filters, a process presumably blind to species’ origins. Yet, exotic plant introductions commonly result in monospecific plant densities not commonly seen in native assemblages, suggesting that exotic species may respond to community filters differently than natives. Here, we tested whether exotic and native species differed in their responses to a local community filter by examining how ant seed predation affected recruitment of eighteen native and exotic plant species in central Argentina. Ant seed predation proved to be an important local filter that strongly suppressed plant recruitment, but ants suppressed exotic recruitment far more than natives (89% of exotic species vs. 22% of natives). Seed size predicted ant impacts on recruitment independent of origins, with ant preference for smaller seeds resulting in smaller seeded plant species being heavily suppressed. The disproportionate effects of provenance arose because exotics had generally smaller seeds than natives. Exotics also exhibited greater emergence and earlier peak emergence than natives in the absence of ants. However, when ants had access to seeds, these potential advantages of exotics were negated due to the filtering bias against exotics. The differences in traits we observed between exotics and natives suggest that higher-order introduction filters or regional processes preselected for certain exotic traits that then interacted with the local seed predation filter. Our results suggest that the interactions between local filters and species traits can predict invasion outcomes, but understanding the role of provenance will require quantifying filtering processes at multiple hierarchical scales and evaluating interactions between filters.     

Ant interactions with native and exotic seeds in the Patagonian steppe: Influence of seed traits,disturbance levels and ant assemblage

Invasive plants may establish strong interactions with species in their new range which could limit or enhance their establishment and spread. These interactions depend upon traits of the invader and the recipient community, and may alter interactions among native species. In the Patagonian steppe we studied interactions of native ant assemblages with seeds of native and exotic plants, and asked whether ant–seed interactions differ with seed types and disturbance levels and whether the amount and type of ant–seed interactions can be predicted if both ant and seed traits are known. To characterize and quantify ant–seed interactions, we offered baits with large seeds of Pappostipa speciosa (native) and medium-sized elaiosome-bearing seeds of Carduus thoermeri (exotic), near and far from a road (high vs. low disturbed areas), and compared ant abundance and composition between areas. Interaction frequency was the highest for C. thoermeri seeds far from the road. Composition of ants interacting with C. thoermeri in these areas differed from that near the road and from that interacting with native seeds. Ant composition and abundance were similar between areas, but some species interacted more with exotic seeds in low disturbed areas. Ant foraging type predicted ant–seed interactions since the abundance of seed harvesters was positively correlated to interactions with P. speciosa, and that of generalists and predators, with interactions with C. thoermeri. The high interaction of ants with exotic seeds in low invaded areas suggests that ant activity could influence plant invasion, either by predating or dispersing seeds of invasive plants.     

The worldwide transfer of ants: geographical distribution and ecological invasions

Aim This is the first comprehensive account of the biogeography of ants transferred and at least temporarily established outside their native habitat. Location Using museum and literature records, I established the distributions of transferred ant species. Methods I used taxonomic and functional groups to assess how geographical spread as a transferred species is affected by taxonomy and life history. Results 147 ant species in forty-nine genera have been recorded outside of their native habitat. The proportion of transferred ants is similar to the number of genera and species in each subfamily. The species-rich subfamily Myrmicinae contains nearly 50% of all transferred species, while many of the species-poor subfamilies have absolutely no transferred species. A disproportionate high number of transferred ants originate from the Neotropical and Oriental biogeographic regions. The Pacific Islands are the recipients of the most transferred ant species. Most transferred ants belong to the CRYPTIC, OPPORTUNIST, and GENERALIZED MYRMICINE functional groups, while there are no recorded transfers of army ants or leaf-cutting ants. Both invasive and human commensal ‘tramp’ ant species are nonrandom subsets of transferred ants. Main conclusions ‘Tramp’ species and invasive species tend to have widespread geographical distributions, and share life history characteristics including queen number, nest structure, and foraging behaviour. Combining observations of functional groups and biogeography may lead to a better understanding of the factors contributing to the spread of transferred species.     

Pathogenic Potential of Soil Fusaria from Malaysian Oil Palm Habitats

A total of 353 Fusarium isolates consisting of 8 species and 2 varieties obtained from the soils of 22 sampling sites in oil palm habitats in Peninsular Malaysia was tested on 2-leaf stage oil palm seedlings. None of the isolates tested produced any symptoms of vascular wilt or other diseases. However, some of the isolates did have an adverse effect on the growth and vigour of the palms. They were found to cause significant reduction in palm growth. Isolates causing a reduction in the growth of the oil palm seedlings were not confined to a certain type of soil or a particular location.     

Ant diversity and distribution in Acadia National Park, Maine

Exotic ant species are a primary threat to ant biological diversity, posing a negative impact to native ant communities. In this study, we examine species richness of ants (family Formicidae) in Acadia National Park, ME, as a fundamental step toward understanding the present impact of the exotic species Myrmica rubra on native ant species. Twelve habitat types were sampled, along six transects, with pitfall traps, visual searching, bait traps, and leaf litter extraction, and the aid of 34 volunteers. We report 42 species of ants in Acadia National Park, comprising five subfamilies (Amblyoponinae, Dolichoderinae, Formicinae, Myrmicinae, and Ponerinae) and 15 genera; the cataloged species represents 75% of the species originally recorded in the area by Procter (1946). Our findings suggest M. rubra is currently not a dominant species throughout the entire island. However, where this species has invaded locally, few competing native species coexist. The species Lasius alienus, Formica subsericea, Myrmica detritinodis, Camponotus herculeanus, Formica argentea, Formica aserva, and Tapinoma sessile occurred most often in our survey. We report the ant species Amblyopone pallipes and Dolichoderus mariae as two new records for the state of Maine.     

Long-term impact of exotic ants on the native ants of Madeira

Abstract.  1. The earliest exotic records for two notorious invasive ants, the big-headed ant ( Pheidole megacephala ) and the Argentine ant ( Linepithema humile ), both come from the Atlantic islands of Madeira, where the two species underwent population explosions in the 1850s and 1890s respectively. Researchers have long assumed that these invaders spread across all of Madeira and exterminated most or all native ants, despite no research actually documenting such impact.
2. Re-examination of first-hand nineteenth century accounts suggest that P. megacephala and L. humile may never have spread beyond coastal lowland areas, representing < 10% of Madeira's land area. In 2002, native ants dominated most of Madeira; P. megacephala and L. humile were restricted to ≈ 0.3% and ≈ 6% of Madeira's land area respectively.
3. Of the 10 native ant species known from Madeira, only one ( Temnothorax wollastoni ) was not present in 1999–2002 surveys. Although exotic ants may have exterminated T. wollastoni , it seems likely that this species still survives.
4. Thus, even after 150 or more years of residence, P. megacephala and L. humile have come to occupy only a small part of Madeira, and appear to have had little impact.
5. Most of Madeira may be too cool for P. megacephala and perhaps too moist for L. humile to dominate. Also, Madeira's vast natural areas may generally lack weedy vegetation that can support high densities of plant-feeding Hemiptera critical for the ecological dominance of invasive ants. Finally, a dominant native ant, Lasius grandis , inhabiting ≈ 84% of Madeira, may actively exclude P. megacephala and L. humile .